"But I hope somebody does just remind people what it means to be conservative and what it means to be decent, we've got to bring that back," Flake said. "If we're going to be a relevant party in the future then we've got to be a decent party."

"This politics of grievance and anger and resentment, you know, you can whip up the base for a cycle or two but it wears thin," he added. "Anger and resentment are not a governing philosophy."

Flake is one of a handful of Republican officials who have earned speculation as a potential 2020 challenger to Trump. He's previously called for a member of the party to challenge the president and hasn't shutdown questions about a 2020 bid of his own.

While Republicans picked up seats in the Senate during Tuesday's midterm election, they also faced a revolt from female, suburban voters who they need if they want to regain a majority in the House and likely to hold onto the White House in 2020.

When asked if the party could flip back congressional seats without making changes, Flake responded: "No, we cant. I'm one who still holds to that autopsy that we did back in '12. ...You can't fight demographics and you've got to appeal to a broader electorate."

Whether Trump can win reelection, Flake said, depends on if Republicans primary the president, as well as who Democrats nominate — a progressive or an individual more to the center of the party.

On Friday, the president lashed out at Flake characterizing him as an "unelectable in Arizona for the 'crime' of doing a terrible job! A weak and ineffective guy!" Flake acknowledged that the president had "in a sense" been able to force him out of office.

"In a sense he did. In that, the price to win a Republican primary was to stand on a stage with the president over and over while he insults minorities and ridicules both Republicans and Democrats and Americans and, you know, goes along with and leads lock her up chants. I couldn't do that. I couldn't do that," Flake said.